Housing
What size is your tank? 1 Gal
What temperature is your tank? 72* (just added heater to bring it up, should be around 80* once it settles in, I'm monitoring it now)
Does your tank have a filter? no
Does your tank have an air stone or other type of aeration? no
Is your tank heated? it is now...
What tank mates does your betta fish live with? none

Food
What type of food do you feed your betta fish? Zoo Med floating betta micro-pellets; I have tried giving him dried blood worms, dapina, & mysis (from the dial-a-treat) but he won't even taste them.
How often do you feed your betta fish? 4-5 pellets twice a day; I try to remove any leftovers

Maintenance
How often do you perform a water change? once a week
What percentage of the water do you change when you perform a water change? 100%
What type of additives do you add to the water when you perform a water change? conditioner

Water Parameters:
Have you tested your water? If so, what are the following parameters? No I don't have anything to test the water

Ammonia:
Nitrite:
Nitrate:
pH:
Hardness:
Alkalinity:

Symptoms and Treatment
How has your betta fish's appearance changed? one eye is swollen and red, white substance appearing on his head, mouth, and now some near his anal fin
How has your betta fish's behavior changed? lethargic, not eating
When did you start noticing the symptoms? eating less and became lethargic 2 weeks ago, as of yesterday he is not eating at all and barely moving
Have you started treating your fish? If so, how? Yes. 100% water changes daily. Added API erythromycin last night, supplemented with epsom salts (2 tsp in the 1 gal bowl) today
Does your fish have any history of being ill? no, although he wouldn't eat at all for the first 2 or 3 weeks I had him (got him in Feb 13)
How old is your fish (approximately)? just under a year

So my betta Kala has been eating very little and acting lethargic for about 2 weeks. Last night, I noticed that he had a swollen red eye. I discovered from other posts on here that this is popeye. He also had some whitish gunk on his head and mouth near that eye. I didn't notice any on his body. I changed the water immediately and got him erythromycin.

Wednesday, the eye looked slightly more swollen, but the white stuff was worse...his head also looks like it might be pulling apart a bit, like perhaps there is an open sore. And it started showing up just slightly on his body, near the anal fin. I added the heater and epsom salt, did another 100% water change, and continued with the erythromycin.

Thursday morning is when I'm making this post... he looked the same as last night... until I came back home at 10AM to find that he has a chunk of skin/flesh hanging off of his head and it looks like his head is just rotting away!! What is this? Help!

If I do need to euthanize... I have no idea how to do that. Can someone point me in the right direction?

Thanks for responding Jaysee, I saw your post elsewhere with a link to how to do it. I suppose I will have to pick up clove oil on my way home from work today. I don't see how Kala could ever recover from missing that much of his face. :(